Systems for providing communication services to groups of system users are well known in the art. For example, a conventional simulcast system incorporating a number of transmission sites is capable of covering a wide geographic area. Each site contains one or more repeater stations. The repeater stations are activated on a common radio frequency to broadcast desired information to users within the covered area.
Trunked radio communication systems can also provide wide area communication service, and can provide this service to specific users as well as specific groups of users. A trunked radio communication system employs both user identifications (IDs) and group IDs. Messages may be directed to intended single users or to groups of users with relative ease.
Current wide area trunked communication system subscriber units affiliate or register with a communication site which provides coverage and service capability in the geographic area. Subscriber units also affiliate with the communication site as an individual of a specific talkgroup. Talkgroups typically consist of many subscriber units of which each subscriber unit -may be affiliated to a unique communication site. Wide area system communication controllers are designed to provide group dispatch services by assigning radio frequency (RF) resources at sites where subscriber units of the service requesting talkgroup are affiliated. When system resources are not available to process a service request to all sites with an affiliated talkgroup member, the communications controller will issue a busy response for the service request. The busy response will be converted to a grant response when a communication resource at all sites with an affiliated talkgroup member becomes available. As wide area communication systems design technology expands and the wide area configuration can support more sites with more subscriber units, the opportunity for wide dispersion of the members of a talkgroup increases. With more talkgroup members affiliated over more sites, the probability of waiting for resource availability increases.
In an attempt to alleviate busy responses due to unavailable communication resources it is known in the art to assign to particular sites and/or particular subscriber units the status of "critical site" or "critical user", respectively. Communication resource assignments in this system are made based upon whether the site is a critical site or the user, located in a non-critical site, is a critical user. Sites that are neither critical nor contain critical users do not have to be available in order to process a communication request. If resources are available in a non-critical site, a resource is assigned; if a resource is not available, the communication request is processed without assigning a resource in the non-critical site. The status of a site as a critical site and a user as a critical user is made during system configuration and is stored as data within a system controller. During a call request, the system controller determines the sites that are designated as critical sites and the sites that contain at least one critical user. A communication resource, if available, is then allocated in each of these sites. A busy response only occurs if a resource is not available in each critical site and in each non-critical site containing a critical user. The requirement that a communication resource be assigned to a critical site will always exist, even if there are no users in that site whose participation in a communication request is required. The requirement that a communication resource be assigned to a non-critical site containing a critical user will also always exist even if the critical user's participation in the communication request is either unnecessary or unwanted. If a resource is not available in these sites, the communication request will be busied until a communication resource becomes available. Also, even if resources are available to reach a non-critical member in a non-critical site, a resource assignment may not be made.
Another known method attempting to manage resource assignment restricts subscriber units from affiliating with particular sites. A subscriber unit attempting to affiliate with a site that it is not authorized for service is denied service. If the site geographically overlaps with a site that the subscriber unit is authorized to use, it may attempt to affiliate with that site. However, the subscriber unit is often outside of the coverage of the authorized site, which is why it is attempting to affiliate with the unauthorized site in the first place. Thus, a subscriber unit in an unauthorized site is denied service entirely and does not negatively effect communication resource allocation. Authorized site information is programmed within the subscriber unit and is slaved within the communication system infrastructure, and in this regard is inflexible. It is also not possible to override the system should it become necessary to reach the user in spite of the site in which the user is located.
Thus, it will be appreciated that known resource allocation methods rely on particulars of the communication site and/or the communication unit. There is a need for an improved method of assigning communication resources in a communication system that allows for communication resource assignment based upon actual site and user service requirements.